Autostereoscopic displays may display two perspective (parallactic) views of an image such that a single viewer at a single position is able to perceive a stereoscopic image form one direction without the viewer having to wear special aid for distinguishing the different images between the correct eyes of the viewer. More advanced types of such displays may provide many more such views (e.g. 9 or 15) so that a viewer can observe several stereoscopic views from different directions or perspectives. Thus, the viewer can move relative to the display to experience a look around effect.
A known type of such autostereoscopic display device comprises a two-dimensional liquid crystal display (LCD) panel having a row and column array of display pixels acting as a spatial light modulator to produce the display of an image that may be a still image or be part of a video. An array of elongate lenticular lenses extending parallel to one another overlies the display pixel array, and the display pixels are observed through these lenticular lenses. The lenticular lenses are provided as a sheet of lenses. Each of the lenses is an elongated semi-cylindrical lens with a cylinder axis along the direction of elongation along which there is no lens surface curvature. The lenticular lenses extend in the column direction of the display panel with their cylinder axis parallel to the column direction and with each lenticular lens overlying a respective group of two or more adjacent columns of display pixels.
In an arrangement in which, for example, each lenticular lens is associated with two columns of display sub-pixels, the display sub-pixels in each column provide a vertical slice of a respective two-dimensional sub-image. The lenticular sheet directs these two slices and corresponding slices from the display sub-pixel columns associated with the other lenticular lenses, to the left and right eyes of a user positioned in front of the sheet, so that the user observes a single stereoscopic image. The sheet of lenticular lenses thus provides a view forming function through its light output directing function.
In other arrangements, each lenticular element is associated with a group of, say, four or more adjacent display sub-pixels in the row direction. Corresponding columns of display sub-pixels in each group are arranged appropriately to provide a vertical slice from a respective two-dimensional sub-image. As a user's head is moved from left to right a series of successive, different, stereoscopic images are perceived creating, for example, a look-around impression in a scene displayed on the device.
The above-described device provides an effective three-dimensional display. However, it will be appreciated that, in order to provide stereoscopic views, there is a necessary sacrifice in the horizontal resolution of the device. In the case of vertical lenticular lenses, the loss of resolution is entirely in the row (horizontal) direction. The use of slanted lenticular lenses as described in U.S. Pat. No. 6,064,424 allows the loss of resolution to be shared between the row and column directions.
There are other known autostereoscopic display designs. For example barriers can be used to block the passage of light, so that different pixels are projected to different eyes of the viewer. Also, other micro lens arrays can be used instead of lenticular lens arrays.
It is also known to provide switchable lenses in the sense that lens function can be switched off, so that a full resolution 2D mode can be provided in addition to the autostereoscopic (3D) mode.